Performance analysis and improvement of air-cooled chiller system with enhanced heat rejection control

The chiller system accounts for a significant proportion of a building’s energy consumption. To improve the performance of air-cooled chillers, more energy-efficient condenser features were investigated in this study, including the variable speed condenser fans (VSCF) and the variable condensing temperature control (VCTC). The thermodynamic models by TRNSYS were developed for an air-cooled chiller with different heat rejection control, and the chiller performance with each heat rejection control was determined. In comparison with the conventional head pressure control (HPC), the chiller COP could be improved by 17.9% with VSCF under HPC, and it could be improved further by up to 51.8% with VSCF under VCTC. The chiller models were applied to determine how the different heat rejection control affected the energy consumption of air-cooled chillers serving an office building. The annual energy saving of the chillers with VSCF under VCTC was 7.7%, indicating the significant energy saving potential by using VSCF and VCTC for air-cooled chillers.